Abstract: A liquid-cooling device includes multiple water blocks and at least one connection tube. Each of the water blocks has a water incoming end, a water outgoing end and a water-receiving space in communication with the water incoming end and the water outgoing end. The connection tube is disposed between each two water blocks. Two ends of the connection tube are respectively connected with the water incoming end of one of the two water blocks and the water outgoing end of the other water block, whereby the water-receiving spaces of the two water blocks communicate with each other via the connection tube. The connection tube has at least one bellows section between two ends of the connection tube. The liquid-cooling device solves the problems of the conventional liquid-cooling device that when the water block is welded, thermal deformation is produced to cause tolerance and the manufacturing cost is higher.